scholarly journals An Ultrasonic Longitudinal Through-Transmission Method to Measure the Compressive Internal Stress in Epoxy Composite Specimens of Gas-Insulated Metal-Enclosed Switchgear

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1248 ◽  
Author(s):  
Zhouyiao Zou ◽  
Yanpeng Hao ◽  
Fangyuan Tian ◽  
Yao Zheng ◽  
Weiming He ◽  
...  
Keyword(s):  
Internal Stress ◽  
Stress Measurement ◽  
Epoxy Composite ◽  
Ultrasonic Method ◽  
Epoxy Composites ◽  
Propagation Time ◽  
Transmission Method ◽  
Acoustoelastic Effect ◽  
Stress Measurements ◽  
Internal Stress Measurement

Situations of internal stress in basin insulators inside gas-insulated metal-enclosed switchgear (GIS) can lead to cracks, which can influence the safety and stability of apparatus. However, there is currently no research on internal stress measurements for composites of GIS basin insulators, and only measurements for surface stress. In this paper, an internal stress measurement method for GIS epoxy composite is proposed using an ultrasonic longitudinal through-transmission technique based on the acoustoelastic effect. An internal stress measurement system is developed to investigate the relationship between the uniaxial compressive internal stress and the velocity of the ultrasonic wave vertical to the stress in epoxy composite within a range of 0–70 MPa, and to calculate the acoustoelastic coefficient of epoxy composite. The effects of system delay are eliminated in measuring the propagation time. Some epoxy composite cuboid specimens with similar materials and using a manufacturing process similar to those of 252 kV GIS basin insulators are synthesized, and the uniformity of the internal stress in cuboid specimens is verified by finite element simulation. The results reveal a linear increase of the ultrasonic longitudinal wave velocity with increasing stress. It has been shown that the average acoustoelastic coefficient of GIS epoxy composites, using the longitudinal waves vertical to the stress, is 4.556 × 10−5/MPa. Additionally, the absolute errors of the internal stress measurements are less than 12.397 MPa. This research shows that the ultrasonic method based on the acoustoelastic effect for measuring the internal stress in GIS epoxy composites is feasible.

scholarly journals Subsurface Stress Measurement in GIS Epoxy Composite by Using LCR Waves

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3725
Author(s):  
Zhouyiao Zou ◽  
Yanpeng Hao ◽  
Yao Zheng ◽  
Weiming He ◽  
Fangyuan Tian ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Internal Stress ◽  
Stress Measurement ◽  
Epoxy Composite ◽  
Propagation Time ◽  
Subsurface Zone ◽  
Wave Technique ◽  
Similar Materials ◽  
Set Up ◽  
Relative Errors

Internal stress in basin insulators of gas-insulated metal-enclosed switchgear (GIS) can lead to cracks, which affects the safe operation of these apparatuses. In this research, we proposed a subsurface internal stress measurement method for GIS epoxy composites. This method is based on an ultrasonic longitudinal critically refracted (LCR) wave technique. In this study, some epoxy composite specimens were synthesized with similar materials and manufacturing processes to those of 252 kV GIS basin insulators. An ultrasonic stress measurement system that utilized the LCR wave technique was set-up to investigate the relationship between stress and LCR wave propagation time, as well as to measure the compressive stress of the epoxy specimen within 0–50 MPa. The results show that LCR wave propagation time linearly decreased when stress increased in the subsurface zone and the acoustoelastic coefficient was −4.95. We found the relative errors of stress measurements to be less than 13%.

Peculiarities of Internal Stress Measurement in Ferromagnetic Materials Using Barkhausen Effect and Other Magnetic Techniques

NDT World ◽  
2018 ◽  
pp. 5-9
Author(s):  
Валерий Венгринович ◽  
Valeriy Vengrinovich ◽  
Дмитрий Винтов ◽  
Dmitry Vintov ◽  
Андрей Прудников ◽  
...  
Keyword(s):  
Internal Stress ◽  
Stress Measurement ◽  
Ferromagnetic Materials ◽  
Barkhausen Effect ◽  
Magnetic Techniques ◽  
Internal Stress Measurement

Influence of Preparing of Specimen on Internal Stress Measurement of Aluminum Alloy Thick Plate

2010 ◽  
Vol 97-101 ◽  
pp. 2658-2663
Author(s):  
Kai Liao ◽  
Yun Xin Wu ◽  
Hai Gong
Keyword(s):  
Stress Distribution ◽  
Internal Stress ◽  
Surface Stress ◽  
Thick Plate ◽  
Stress Measurement ◽  
Stress Gradient ◽  
Real Surface ◽  
Measurement Results ◽  
Layer Removal Method ◽  
Internal Stress Measurement

The cut, a main preparing means of specimen, will cause a difference in stress distribution between thick plate and the specimen, so this article focuses on the topic of evaluating impact of the cut on stress measurement results. Firstly, the real surface stress distribution of the plate and specimen were determined by X-ray diffraction (XRD) and FEM. Secondly, according to the specimen dimension and machining procedure, the influence of the cut on internal stress measurement is obtained and compared with the FEM results. The conclusions are as follows: (1) the normal stress of cut plane steeply decreases and the stress gradient descends along with distance away from the cut. The range of distance is approximately one-thickness of specimen. (2) In order to obtain stable and reliable results, the plane size of specimen is taken three times larger than the thickness. (3) The milling processing of layer removal method (LRM) can change the surface stress state of specimen, but the machining effects on residual stresses can be removed by properly choosing milling parameters.

Research of Correctness on Internal Stress Measurement in Aluminum Alloy Thick Plate

2011 ◽  
Vol 383-390 ◽  
pp. 3272-3278
Author(s):  
Kai Liao ◽  
Yun Xin Wu
Keyword(s):  
Aluminum Alloy ◽  
Internal Stress ◽  
Thick Plate ◽  
Measurement Problem ◽  
Stress Measurement ◽  
Experimental Conditions ◽  
Total Uncertainty ◽  
Layer Removal Method ◽  
Simulation And Experiment ◽  
Internal Stress Measurement

It’s necessary to research and analyze the correctness of internal stress measurement, in order to effectively deal with the measurement problem of stress field and rightly describe the distribution character of stress in aluminum alloy thick plate. Firstly, the total uncertainty of stress calculation in layer removal method (LRM) is determined by experimental error and model error, and less than ±10MPa, in which the accuracy of experiment is high. Secondly, in the integral calculation of LRM, a modified function is proposed by the multi-methods of simulation and experiment, and can compensate the deviation resulted from unpredictable error for experimental conditions. Then the multi-methods achieve the value of X-ray surface stress, simulation calculation and experimental results to consistent, the correctness of experimental calculation is enhanced. The research presents that the LRM can exactly describe distribution of internal stress in thick plate under special experiment conditions.

scholarly journals Measurement of Stress Optic Coefficient for Thermal Barrier Coating Based on Terahertz Time-Domain Spectrum

Coatings ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1265
Author(s):  
Zong Wang ◽  
Yanheng Zhang ◽  
Ning Lu ◽  
Zhiyong Wang ◽  
Wei Qiu
Keyword(s):  
Residual Stress ◽  
Internal Stress ◽  
Thermal Barrier Coating ◽  
Time Domain ◽  
Stress Measurement ◽  
Thermal Barrier ◽  
Terahertz Time Domain Spectroscopy ◽  
Mechanics Model ◽  
Barrier Coating ◽  
Internal Stress Measurement

The residual stress introduced inside the thermal barrier coating (TBC) top coating during manufacturing and service processes is one of the main causes of thermal barrier failure. Therefore, a nondestructive and accurate measurement of the residual stress in top coating is essential for the evaluation of TBC life. The terahertz time-domain spectroscopy (THz-TDS) technique, which is based on the calibration or measurement of the stress optical coefficients of the measured materials, is applicable to the measuring of internal stress of nonmetal materials. In this work, to characterize the internal stress in TBC, the stress optic coefficient of the TBC top coating was measured by reflection-type THz-TDS. First, the mechanics model for the internal stress measurement in a TBC top coating was derived based on the photoelastic theory. Then, the THz time-domain spectra of TBC specimens under different loadings were measured in situ by a reflection-type THz-TDS system. Finally, the unimodal fitting, multimodal fitting and barycenter methods were used to carry out the data processing of the THz time-domain spectral-characteristic peaks. By comparing the processed results, the results using the barycenter method were regarded as the calibrated stress optical coefficient of the TBC due to the method’s sufficient accuracy and stability.

Influence of Milling Process on Internal Stress Measurement in Thick Plate

2011 ◽  
Vol 314-316 ◽  
pp. 1411-1414
Author(s):  
Su Ming Li ◽  
Kai Liao ◽  
Pei Yin Luo
Keyword(s):  
Internal Stress ◽  
Thick Plate ◽  
Stress Measurement ◽  
Experimental Testing ◽  
Milling Process ◽  
Scientific Experiments ◽  
Layer Removal Method ◽  
Stress Layer ◽  
Fitting In ◽  
Internal Stress Measurement

Layer removal method is executed by milling process, which may causes deformation and stress change of sample in aluminum alloy thick plate. Through error assessment about the experimental testing process involved milling, the milling stress layer is very thin and fail to change the whole stress dietribution of sample under some technique. Because many times of the loading - unloading operation will increase the deformation error of sample, per-depth of milling is should not be too small for the enhancement of accuracy of data fitting in stress measurement. Finaly, under the conditions of reasonable milling process and scientific experiments, influence of milling process on internal stress measurement can be ignored.

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